Method for forming an electroconductive coating resistor

ABSTRACT

A CAPLESS ELECTROCONDUCTIVE COATING RESISTOR FORMING METHOD. THE RESISTOR DIELECTRIC SUBSTRATE IS FORMED ON A CONTINOUS BASIS, PASSED BETWEEN FORMING ROLLS TO IMPART THEREIN GROOVES AND NOTCHES, COATED WITH RESISTIVE MATE RIAL, AND THEREAFTER SEPARATED INTO INDIVIDUAL RESISTO BLANKS. WIRE LEADS ARE ATTACHED DIRECTLY TO THE BLANDS BY WRAPPING THEM ABOUT THE BLANKS WITHIN THE PREFORMER GROOVES AND IN ELECTRICAL CONTACT WITH THE RESISTIVE MATERIAL COATING.

0611.. 12, 1971 LOOSE 3,611,560

- METHOD FOR FORMING AN ELECTROCONDUCTIVE COATING RESISTOR Original Filed Dec. 27. 1968 2 Sheets-Sheet l 24 26 h 1m 28 22 I 28 2:5 26 -3Q -I l 29 ---20 I 24 HI lllll -2o 36 F lg 2 INV 0. Y Fl fiuenfer H. L332;

AT TORNEY G. H. LOOSE 3,611,560

METHOD FOR FORMING AN ELECTROCONDUCTIVE COATING RESISTOR Oct. 12, 1971 2 Sheets-Sheet 2 Original Filed Dec. 27. 1968 INVENTOR. fiwemer 100w TTORNEY United States 3,611,560 METHOD FOR FORMING AN ELECTRO- CONDUC'I'IVE COATING RESISTOR Guenter II. Loose, Webster, N311, assignor to Corning Glass Works, Corning, N.Y.

Original application Dec. 27, 1968, Ser. No. 787,530, now Patent No. 3,544,948, dated Dec. 1, 1970. Divided and this application Dec. 1, 1969, Ser. No. 881,186

Int. Cl. 1101c 7/00, 17/00 U.S. Cl. 29-4520 6 Claims STRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 787,530, filed Dec. 27, 1968, now U.S. Pat. No. 3,544,- 948.

BACKGROUND OF THE INVENTION 'Electroconductive coating resistors have been heretofore made by forming a dielectric resistor substrate, ordi narily in cylindrical shape, applying thereto a film of elec troconductive or resistive material, and thereafter cutting the dielectric substrate into individual resistor blanks. The resistor blanks would have a coating of silver or other conductive material applied to the ends thereof, be fired to fuse the conductive material, and the blank would thereafter be spiralled if desired to increase the resistance value thereof. A metallic cap with a lead attached thereto would be fitted over the ends of the resistor blank so that electrical continuity would be made between a lead and the electroconductive or resistive material. The resistor would then be suitably coated or encapsulated. Such a method would require the diameter of the dielectric substrate to be maintained within close tolerances so that the cap could thereafter be properly fitted onto the ends thereof. The lead and cap combinations result in an expensive means for providing electrical continuity between the electroconductive coating and the leads. In addition, the caps increase the diameter of the overall device. Furthermore, the silver or conductive material applied to the individual resistor blanks requires expensive and bulky silvering machines. Lastly, the method requires expensive capping machines to fit the caps over the ends of the resistor blanks and cutoff machines for cutting off the individual resistor blanks from the continuous substrate material.

SUMMARY OF THE INVENTION The objects of the present invention are to provide a simplified, direct, and inexpensive method of manufacturing electroconductive coating or film resistors which are capless, rugged, and inexpensive, and which overcome the hereinabove noted disadvantages.

Briefly, according to the present invention, a capless electroconductive coating resistor can be formed by first forming a substantially cylindrical dielectric subtra'te, and thereafter passing the substrate between a pair of forming rollers whereby the substrate is peripherally notched at predetermined places to form a plurality of resistor blanks. The forming rolls also form a peripheral groove adjacent each end of each resistor blank and a longitudinal aten notch extending from each of the peripheral grooves to the end of each resistor blank. A coating of electroconductive or resistive material is applied to the substrate and, if desired, a conductive coating is applied in and about the grooves at the terminal ends of the resistor blank. The coated continuous substrate so formed is then separated into individual resistor blanks which may thereafter be spiralled to increase the resistance thereof, if desired or necessary. Wire leads .are attached to the individual resistor blanks by wrapping a wire lead about each groove of the resistor blanks in such manner as to make electrical contact with the resistive material or conductive coating and thereafter extending the leads outwardly from the resistor blank along and within the longitudinal notches.

Additional objects, features, and advantages of the present invention will become apparent to those skilled in the art from the following detailed description and the attached drawings on which, by way of example, only the preferred embodiment of this invention is illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation of an apparatus illustrating the manufacture of capless electroconductive coating resistors of the present invention.

FIG. 2 is an elevation of the substantially continuous, cylindrical dielectric substrate of the present invention after passing between forming rollers.

FIG. 3 is a fragmentary oblique view of a resistor blank formed in accordance with this invention.

FIG. 4 is a cross sectional view of the resistor blank of FIG. 3 taken along line 4-4 thereof.

FIG. 5 is a cross sectional view of the resistor blank of FIG. 3 taken along line 5-5 thereof.

FIG. 6 is a fragmentary oblique view of a resistor blank of the present invention having a lead wire attached thereto.

DETAILED DESCRIPTION For the purposes of simplicity, the present invention will be described in connection with forming a capless resistor having a glass dielectric substrate and an electroconductive coating of metallic oxide or the like. As is readily understood, the present invention is in no way limited to such materials. Dielectric materials suitable for the present purposes may be glass, glass-ceramics, ceramics, plastics, and the like. For a clear understanding of metallic oxide films as resistive or electroconductive c0atings, their characteristics, and one example of their application, reference is made to U.S. Pats. Nos. 2,564,706 and 2,564,707 issued to John M. Mochel.

Reference is made to FIG. 1 wherein there is shown a glass melting tank 10 having an orifice 12. A glass cylindrical cane or rod 14 is drawn from the tank and caused to pass between a pair of forming rollers 16 and 18. These rollers are placed in such relationship to the orifice that the glass cane at the rollers has a temperature above the softening point thereof whereby the cane may be suitably deformed. Referring additionally to FIG. 2, there is seen a fragmentary section of deformed cane 20 in which there has been formed by rollers 16 and 18 a pair of peripheral notches 22 which define the length of an individual resistor blank 24. Also formed on cane 20 by the rollers are a pair of peripheral grooves 26 adjacent the terminal ends of the resistor blank and a pair of longitudinal notches 28 extending from peripheral grooves 26 to the ends of resistor blanks 24. As is readily understood, the deformation of the cane or resistor substrate as illustrated in FIG. 2 would be repeated along the entire length thereof.

Formed cane or resistor substrate 20 is then passed through a suitable apparatus 30* where an electroconductive coating would be continuously applied to the entire length thereof. An electroconductive coating such as the metallic oxide film hereinabove noted in connection with the Mochel patents, may be applied by means of iridizing as therein described. After the electroconductive film is applied, which film shall thereafter comprise the resistive portion of the ultimate resistors, the cane or substrate 20 is then passed through a conductive coating apparatus 32 wherein a coating of conductive material such as silver, copper or the like is applied in the form of a paste to the terminal ends of the individual resistor blanks. For example, such conductive coating would be applied in the peripheral groove of resistor blank 24 and also the terminal portion thereof, if desired. If the conductive coating is applied as a paste or the like, the coated cane is then passed through a drying apparatus 34 to permit the conductive coating to be firmly adhered to the resistor blank. As will be readily understood, such a conductive coating improves the electrical conductivity between the subsequently connected leads and the electroconductive film comprising the resistive portion of the resistor. Such a conductive coating may be omitted if sufficient electrical conductivity may be obtained between the electroconductive film and the wire lead by direct ohmic connection.

The formed and coated cane is then separated into individual resistor blanks by means of a suitable break off device 36 which breaks off each resistor blank 24 at the peripheral notches 22. These notches are initially formed with sufficient depth so as to reduce the strength at that point permitting easy break off by means of a projecting arm operated by a suitable controlling device, such as a solenoid or the like.

Referring to FIG. 3 there is shown a terminal portion of a resistor blank 24 after it has been separated from substantially continuous cane 20. FIG. 4 illustrates a cross section of the resistor blank 24 with electroconductive film 38. FIG. 5 illustrates a cross section of a resistor blank 24 taken through the terminal portion thereof. Shown in this view is electroconductive film 38 and a conductive film 40.

Where it is desired to increase the resistance value of the ultimate resistor, the electroconductive film may be spiralled by any method well known in the art whereby the length to width ratio as well as its resistance is increased.

Referring to FIG. 6 there is shown a fragmentary view of a resistor blank 24 having a wire lead 42 attached thereto by wrapping one end of the wire lead about groove 26 to make electrical contact with electroconductive film 38 through conductive film 40, if present. After the lead is wrapped around groove 26, it is extended outwardly parallel to the longitudinal axis of the resistor blank and fitted within longitudinal notch 28.

As is well known in the art, the completed resistor may thereafter be encapsulated by applying a coating of dielectric material over the surface thereof by any means such as potting, molding, spraying, and the like, such that only the extending portion of the leads remain exposed.

The present invention was described in connection with drawing a glass cane or substrate from a glass tank.

4 Another embodiment of the present invention involves reheating. and redrawing a larger size rod into a rod of any suitable diameter. Such a redrawn rod would thereafter be processed as heretofore described.

Although the present invention has been described with respect to specific details ofcertain embodiments thereof, it is not intended that such details be limitations upon the scope of the invention except insofar as set forth in the following claims.

-I claim:

1. A method of manufacturing resistors comprising the steps of:

forming a substantially continuous and cylindrical dielectric substrate, passing said substrate between a pair of forming rolls whereby the substrate is peripherally notched at desired intervals to define a plurality of resistor blanks and to form a peripheral groove adjacent each end of each resistor blank,

applying an electroconductive coating to such formed continuous dielectric substrate,

separating individual resistor blanks from the continuously formed substrate,

wrapping a wire lead about and within each groove of said resistor blank so as to make electrical contact with said electroconductive coating, and

thereafter extending said leads outwardly from said resistor blank.

2. The method of claim 1 further comprising the step of forming a longitudinal notch in said resistor blank extending from each said peripheral groove to the end of said blank and, thereafter, when said leads are extended outwardly from said resistor blank disposing at least a portion of said lead within said longitudinal notch.

3. The method of claim 1 further comprising the step of applying a band of conductive material in and about the peripheral groove and terminal portion of said resistor blank.

4. The method of claim 1 further comprising the step of spiralling the electroconductive coating to increase the resistance thereof.

5. The method of claim 3 wherein said conductive material is applied in the form of a paste further comprising the step of drying said conductive material.

6. The method of claim 1 wherein individual resistor blanks are separated from the substantially continuous substrate by breaking off said blanks at the peripheral notches.

References Cited UNITED STATES PATENTS 1,929,396 10/1933 Benkelman 338332 X 2,487,057 11/1949 Kohring 29619 X 2,798,140 7/1957 Kohring 338137 2,816,996 12/1957 Kohring 29619 X 3,107,179 10/1963 Kohring 29--621 X JOHN F. CAMPBELL, Primary Examiner V. A. DI PALMA, Assistant Examiner U.S. Cl. X.R. 29-610, 621 

